This invention relates to a gas driven gyroscope (gyro) with an integrally contained gas source. More particularly it relates to improvements in gas driven gyroscopes which reduce internal friction in order to extend the rundown time or maintain higher speeds of the rotor during a specified time.
Gas driven gyroscopes with integrally contained gas sources are known which have a gas driven reaction rotor in one chamber and compressed inert gas in another chamber. Gas is released from one chamber by means such as puncturing a thin wall between the chambers. The gas, when released, flows through the hollow bore of the rotor shaft and outwardly through reaction passages in the rotor to cause it to spin. Changes in the gas pressure may also be used to uncage the gyroscope gimbals after the rotor is spinning. Such gyroscopes are sometimes called pyrotechnic gyros because pyrotechnic techniques are frequently used to puncture the wall.
An example of the foregoing type of gas driven gyroscope is detailed in U.S. Pat. No. 3,393,569, issued July 23, 1968, now assigned to the present assignee. The U.S. Pat. No. 3,393,569 is incorporated herein by reference and any of the various species of gas driven gyros shown in that patent might employ the improvement of the present invention.
One advantage of a gas driven gyro, as compared to a spring driven gyro, is that the gas driven gyro has a high ratio of usable energy in relation to its volume and weight. The potential energy in the compressed gas is quickly translated to rotational kinetic energy of the spinning rotor. The "rundown" of the rotor refers to the gradual decrease in rotor speed over time after the gas is expelled through the rotor passages. Various loss factors affect the rundown of such gyros. The most significant of these factors relates to energy absorbed by the gyro's interaction with that gas which remains in the gyroscope after gas release is completed. This invention is directed to the reduction of such air friction losses.
One such air friction loss is caused by the reaction rotor acting as a pump rather than as a reaction turbine and acting to suck gas through the end of the shaft to pump it out the rotor exhaust ports. This reduces kinetic energy and causes more rapid slowing of the rotor. This problem is specifically addressed by U.S. Pat. No. 4,271,709, issued Jan. 9, 1981, now assigned to the present assignee and incorporated herein by reference. That patent discloses a poppet valve which prevents such pump action. The prevention of such pumping, of course, does not eliminate other air friction losses from the gyroscope which is spinning at high speeds, preferably in excess of 30,000 RPM.
Accordingly, one object of the present invention is to improve gyroscope performance. It is therefore an object to provide an improved gas driven gyroscope with an extended rundown time, or having a higher average speed during a specified rundown time. Another object of the invention is to provide an improved gas driven gyroscope with reduced losses during rundown. Another object of the invention is to provide a gas driven gyroscope in which running friction is reduced during rundown. It is a further object to provide the gyroscope in which air is provided to the gyroscope in order to provide kinetic energy for the gyroscope rotor, and the air is evacuated from the gyroscope after initial run-up in order to extend rundown time of the gyroscope particularly at high rotor speeds. It is therefore an object to reduce air friction in a gas driven gyro.